A bag contains $10$ red balls, $8$ green balls, and $5$ blue balls. If a ball is randomly chosen, what is the probability that it is not red?
Explanation: There are $10 + 8 + 5 = 23$ balls in the bag. There are $10$ red balls. That means $23 - 10 = 13$ are not red. The probability is $ \frac{13}{23}$.